International economic uncertainty has expanded in Trump’s second term. In April he announced the highest U.S. tariffs in a century, only to suspend them for 90 days to permit negotiations for new trade deals. Only the United Kingdom has achieved a “framework” of a deal, while China and the U.S. have agreed to a trade war truce while they pursue a broader negotiation.

The G-7 has historically served as a forum for the free world’s strongest economies to talk about their shared interests on trade, security and climate policy — but Trump has upended those interests by imposing tariffs, arguing for the annexation of Canada as the 51st state and threatening to use military force to take over Greenland, a mineral-rich island territory controlled by Denmark.

Even on the conflict between Israel and...